This invention relates to water purification and more particularly to an apparatus for subjecting fluids to ultraviolet (UV) light. The apparatus may be used for water sterilization and is intended for point-of-use on demand application. The invention relates generally to devices and methods for disinfecting water and, more particularly, to a portable, low-cost system for disinfecting water using ultraviolet light. This disclosure relates generally to devices and methods for disinfecting water and, more particularly, to a portable, low-cost system for disinfecting water using ultraviolet light.
In both urban and rural areas of developing countries, the main limitation for ensuring good quality drinking water to the population is the absence of what developed countries call “tap water”.
Urban areas of developing countries do not have access to continuous flow of water in their potable distribution system; instead, urban households receive only a few hours of water per day, and not every day. As a result, buildings in urban areas are equipped with storage tanks that are filled whenever there is flow in the municipal water pipes. Those tanks can be roof tanks or underground cisterns. They range in volume between 200 and 1000 gallons storage capacity. Therefore, in developing countries, opening a faucet means receiving water from a tank where water has been stagnant for a few days, possibly silted and contaminated with bacterial growth.
Consequently, most urban households in developing countries do not drink water from their faucets, they use it solely for washing, bathing, and sometimes cooking. For drinking, urban families purchase “purified water”, typically sold in 5 gallon jugs that cost around 1 dollar. The 5 gallon jugs are heavy and cumbersome and require some kind of dispenser for serving the water. Typical dispensers are either plastic or ceramic large-mouth containers, and 5-gal jugs are flipped 180 degrees on those containers so as to rest neck-down. The dispensers are equipped with a regular plastic spigot to conveniently serve water. From a study conducted in 2009 in a medium-size city of Mexico, namely La Paz, Baja California Sur, it was determined that 95% of the 150 urban families interviewed were using 5-gal purified water jugs and dispensers in their households for drinking water. In the same study, water quality tests were conducted to measure concentration of bacteria, i.e. total coliform and fecal coliform bacteria, in both unopened 5-gal jugs and household dispensers. It was found that there was zero bacterial contamination in the 5-gal jug samples. However 26% of these spigoted dispensers had total coliform bacteria and 11% had fecal coliform bacteria in their drinking water.
Dispensers therefore seem to promote recontamination of the water. Sources of recontamination include typical handling and transport of jugs. Purified water jugs are oftentimes delivered at the back of pick-up trucks, by a person carrying it on his shoulder to the house and placing it onto the spigoted dispenser. Dust and fumes during transport and unwashed hands while handling 5-gal jugs are therefore likely pathways for bacteria to reach the inside of the drinking water dispensers.
Having examined the water situation in urban areas of developing countries, it can easily be imagined how the problem is magnified in rural areas. There are no faucets and no water distribution infrastructure in most rural communities of the developing world. Water is carried from the wells or springs to the house in buckets or other containers. In the best scenario, there might be a hose or pipe conducting water by gravity from a spring or tank to communal faucets. In a study conducted in 2005 in Baja California Sur with the National Water Commission of Mexico, samples of 500 water sources in rural communities and determined that 42% of them had fecal contamination. In the same study, samples were taken from 500 household water containers and found that 54% had fecal contamination. Household containers are indeed generally more contaminated than water sources in rural communities. Providing a “safe” water source is therefore not enough since rural families have no “tap water” and will continue to store water in unsafe containers. In another study of 30 existing water filters installed by aid agencies and non-profit organizations, it was found that 36% of water filters had total coliform bacterial contamination in the stored filtered water, one of the filters actually having had a higher bacterial concentration in the filtered water compared to the source water. This can be explained by lack of maintenance and cleaning of the filter, poor hygienic conditions in the households such as dirt floors and dusty homes, handling of filters with unwashed hands, and presence of animals in the households (for example, a chicken sitting on top of a bucket water purifier).
From the foregoing description of the water situation in developing countries it can be concluded that safe drinking water can only be provided at the point-of-use. But that is not enough, because point-of-use water filters, if they involve storage of the filtered water, can themselves become contaminated. Safe drinking water therefore requires not merely point-of-use purification, but actually no-storage instantaneous point-of-use purification. This is the main motivation beyond the here-presented invention.
Prior point-of-use water purification devices for developing countries typically involve storing filtered water within the device, such as the various types of ceramic pot filters and ceramic candle filters (Potters-For-Peace, Katadyn) which are prone to recontamination of the filtered water, especially if adequate maintenance is not provided to the filter after a few months of use. The germicidal chemicals used in ceramic filters, typically iodine or silver, are lost after a year of use, but users have no way to know when replacement of the ceramic element is necessary, they therefore continue using their device for many years. This leads to the filter being a source of contamination instead of a means of sterilization, as was observed during the aforementioned water sampling campaign, where filtered water had sometimes more bacteria than the source water.
Boiling is another typical means of sterilizing water, but the boiled pot of water left standing in the kitchen is used by family members throughout the day, and water is retrieved from the pot by dipping cups which leads to quick recontamination of the boiled water. A simple experiment was conducted in a rural household of Mexico to measure the recontamination time for boiled water: at 10 am, a pot of water was boiled and a sample was taken to ensure it had zero bacterial contamination; samples were then taken every 30 min, and it was observed that recontamination by bacteria occurred at the fourth sample, i.e. at 11:30 am. Only one hour and 30 minutes was necessary to recontaminate boiled water left standing in a kitchen in a typical rural household scenario.
Chlorine or iodine drops are another means of sterilizing water in developing countries. Chemical disinfection is difficult to implement at the household level, since rural families strongly reject the taste of those disinfectants described as unhealthy to ingest. Short shelf life of those disinfectants require frequent buying which is oftentimes impossible for isolated communities, who prefer to spend the few dollars of their monthly budget on food and other items.
Other devices have employed ultraviolet light to sterilize water for use in developing countries, such as the UV water purification system described in U.S. Pat. No. 7,361,904 and the UV water disinfector described in U.S. Pat. No. 5,780,860. The former presents a major problem observed during monitoring of 1,500 units installed in rural Mexico between 2006 and 2008. The disinfection chamber is prone to silting since fine sediments contained in water accumulate over time and grow to a thick “mud-type” layer. Water passing in the bottom chamber is therefore not sterilized properly by UV radiation source since bacteria can easily hide in between mud particles before reaching the outlet where the user obtains water. Observation of the use of the aforementioned UV water purification system led to the conclusion that a water sterilization device intended for developing countries cannot rely on maintenance performed by a user, since many users will not clean or maintain their water sterilization device, at least not as expected by the inventor of the device. The UV water disinfector described in U.S. Pat. No. 5,780,860 is another sterilization device intended for use in developing countries at the village scale. The major issue with village-scale sterilization devices is recontamination of the water during transport and storage. Villagers will walk a certain distance to the location of the sterilization system to obtain water, or will have someone deliver sterilized water to their homes. But if sterilized water is transported or stored in unclean containers, or if water is retrieved by dipping cups where hands can come in contact with sterilized water, there is a significant risk of recontamination within a few hours of obtaining sterilized water.
Other devices using ultraviolet light to sterilize water have been invented for use in modern homes of developed nations. The UV water purifying devices described in U.S. Pat. Nos. 6,909,101; 5,843,309; and 4,280,912 are faucet-type UV sterilizing systems. These devices are specifically manufactured for developed country household plumbing systems and would not be easily adapted to rural households in the developing world. These devices also have elongated conduits between the UV radiation source and the water outlet which can promote growth of bacteria between each use. Droplets of water remaining in the conduit between the UV sterilizing chamber and the water orifice can promote bacterial growth which would not be sterilized by subsequent uses of the device. Other UV sterilizing devices are counter-top water purification devices such as those described in U.S. Pat. Nos. 6,451,202; 6,726,839 and 5,445,729 involving multiple steps of filtering and sterilizing with a UV radiation source prior to dispensing at a spigot. Those units are complicated and costly, typically in the hundreds of dollars, and they are therefore neither affordable nor easily serviceable by families in developing countries. The counter-top units pose the same problem as the faucet-type ultraviolet systems described above, because they also possess an elongated conduit between the UV sterilization chamber and the water outlet which creates a potential recontamination hotspot that is not easily accessible for cleaning between each use.
The present invention is a simple, compact, affordable, maintenance-free and recontamination free ultraviolet purification spigot that resolves many of the challenges observed in other water purification devices intended for developing countries. By placing the UV light immediately adjacent to the outlet orifice of the water, there is no recontamination risk along conduits or in storage units and the user is able to sterilize just the amount that is needed, be it a glass of water to drink or a pot of water to bath a child. The small size of the device is an essential characteristic of this invention which will greatly enhance its distribution potential in rural areas of developing nations as hardware stores in villages or county capitals will be able to carry this device in their inventory among other similar-sized items such as bulbs, batteries, and flashlights. This will eliminate the need for humanitarian-type distribution schemes by governments, aid agencies or non-profit organizations which are generally one-time campaigns that do not establish distribution channels for long-term supply of replacement parts. As a final note, the present invention provides a great opportunity for creating a national water solidarity campaign between urban and rural areas. Such a campaign can be conceived such that, for every UV spigot sold in urban markets, one UV spigot can be subsidized for a rural family.
Every day, an estimated 3,000 to 6,000 die worldwide due to infections from waterborne bacteria. Death typically results from acute dehydration, malnutrition, or other related complications. The majority of victims are young children and older people that live in economically impoverished countries. In these regions, contaminated surface water sources and poorly functioning municipal water distribution systems lead to the transmission of waterborne bacterial diseases. Although the problem is particularly bad in impoverished countries, population groups in developed countries, such as residents in remote rural areas of the United States with poor water treatment and delivery systems, are also at risk. In addition, campers and hikers who do not have access to treated water also commonly fall victim to waterborne bacterial infections.
Conventional centralized water treatment and distribution systems can be very expensive and take years to complete. Furthermore, it is often impractical to provide centralized water treatment in sparsely populated areas. Therefore, to provide the at risk groups with potable water requires innovative practical solutions such as, for example, point-of-use disinfection. In one disinfection method, ultraviolet (“UV”) radiation having wavelengths in the range of 200 to 300 nm may be used to kill disease-carrying microorganisms in water. UV radiation has been found to deactivate a broad spectrum of pathogenic contaminates from amoebic sized microorganisms to bacteria, algae and viruses. Water purification by ultraviolet radiation provides numerous advantages over other currently available water treatment methods. For example, UV water purification systems do not require chemicals nor do they require expensive filters.
Existing UV water purification systems are often large installed flow-through systems serving a large number of people. However, in recent years, a number of smaller portable UV water purification systems have become available for use by individuals. Portable UV water purification systems use fluorescent tubes for emitting UV light into the water. A quartz cover is typically provided around the fluorescent tube to protect the light source from mechanical shock and to electrically insulate the light source from the water being disinfected. Quartz covers are commonly used because it has been found that quartz is transparent at germicidal UV wavelengths, such as, around 254 nm. However, quartz covers are very expensive and thereby substantially increase the manufacturing cost.
Existing UV water purification systems also include electronic circuitry for driving the fluorescent tube. The circuitry is typically configured to drive the fluorescent tube using a “cold-cathode” striking method. In this method, a high voltage (e.g., 400-500V RMS) is applied to the anode and cathode terminals of the fluorescent tube. The voltage must be high enough to produce ionization with the anode and cathode terminals at room temperature (i.e., hence “cold-cathode”). In one common cold-cathode striking method, an H-bridge driven, capacitively tuned, step up transformer circuit is used to drive the fluorescent tube with an AC power input. Unfortunately, this type of electronic circuitry is expensive to manufacture, thereby driving up manufacturing costs and making the system prohibitively expensive for many applications. As a result, UV water purification systems and, more particularly, portable UV systems have not met with great commercial success.
Due to the complexity and high costs associated with existing UV water purification systems, an urgent need exists for an improved water purification system that requires fewer components and is easily affordable to large segments of the population. It is desirable that such a system be rugged in construction and easily transportable for disinfecting drinking water in regions wherein water purification is not available. It is also desirable that such a device be lightweight, compact and easy to use. The present invention addresses these needs.
Every day, thousands die worldwide due to infections from waterborne bacteria and viruses. Death typically results from acute dehydration, malnutrition, or other related complications. The majority of victims are young children or elderly people that live in economically impoverished countries. In these regions, contaminated surface water sources and poorly functioning municipal water distribution systems lead to the transmission of waterborne bacterial and viral diseases. Although the problem is particularly bad in impoverished countries, population groups in developed countries, such as residents in remote rural areas of the United States with poor water treatment and delivery systems, are also at risk. In addition, campers and hikers who do not have access to treated water also commonly fall victim to waterborne bacterial and viral infections.
Conventional centralized water treatment and distribution systems can be very expensive and take years to construct. Furthermore, it is often impractical to provide centralized water treatment in sparsely populated areas. Therefore, providing at-risk groups with potable water requires innovative practical solutions such as, for example, point-of-use disinfection. In one disinfection method, ultraviolet (“UV”) radiation having wavelengths in the range of 200 to 300 nm are used to kill disease-carrying microorganisms in water. UV radiation has been found to deactivate a broad spectrum of pathogenic contaminates from amoebic-sized microorganisms to bacteria, algae and viruses. Water purification by ultraviolet radiation provides numerous advantages over other currently available water treatment methods. For example, UV water purification systems do not require chemicals nor do they require expensive filters.
Existing UV water purification systems are often large installed flow-through systems serving a large number of people. However, in recent years, a number of smaller portable UV water purification systems have become available for use by individuals. Portable UV water purification systems use fluorescent tubes for emitting UV light into the water. A quartz cover is often provided around the fluorescent tube to protect the light source from mechanical shock and to electrically insulate the light source from the water being disinfected. Quartz covers are commonly used because it has been found that quartz is transparent at germicidal UV wavelengths, such as, around 254 nm.
Existing portable UV water purification systems also include electronic circuitry for driving the fluorescent lamp. These devices and their circuits are often heavy and include multiple batteries in order to power the device and as such will sink if released into the liquid being treated. Furthermore, they must be affixed to the containers of liquid they are treating or otherwise held in place therein. As a result many containers are not viable candidates for treatment with such a device. Finally, point-of-use devices are generally small and cannot reach into the depths of a large container, limiting their usefulness to small storage and drinking containers.
Due to the costs associated with existing UV water purification systems, a need exists for an improved water purification system that requires fewer components and is easily affordable to large segments of the population. It is desirable that such a system be rugged in construction and easily transportable for disinfecting drinking water in regions where water purification is not readily available. It is also desirable that such a device be lightweight, compact, and easy to use. The present invention addresses these needs.